The present invention relates to a novel thermoplastic resin composition having high heat resistance coupled with high impact resistance.
While acrylonitrile-styrene copolymer compositions comprising a rubber (hereinafter abbreviated to ABS resins) are widely used because of their excellent processability and high impact resistance, they are still accompanied by the disadvantageous problem of a low heat distortion temperature. In order to solve this problem, various resin compositions have been proposed, for example, as follows.
(1) A composition wherein styrene (St) which is a monomer to be grafted onto a rubber together with another monomer acrylonitrile (AN) is replaced by .alpha.-methylstyrene (.alpha.-Mest) (U.S. Pat. No. 2,908,661).
(2) A composition comprising a blend of an ABS resin and an .alpha.-Mest/AN copolymer (Japanese Patent Pub. No. 18194/1960).
(3) A composition obtained by grafting onto a rubber St and AN, and then .alpha.-Mest and AN (Japanese Patent Pub. No. 13616/1967).
(4) A composition comprising a blend of an ABS resin and an .alpha.-Mest/methyl methacrylate (MMA)/AN copolymer (Japanese Patent Pub. No. 18016/1970, No. 33304/1970 and No. 15902/1969).
(5) A composition comprising an .alpha.-Mest/MMA/AN copolymer and a graft copolymer obtained by graft-polymerizing MMA, St and AN onto a rubber (Japanese Patent Pub. No. 37415/1971).
The heat resistance of resins can thus be improved by the use of .alpha.-Mest and MMA in place of conventional resin constituents, but this measure is still inadequate, and there has been an urgent demand for ABS resins having higher heat resistance.